In general, in an engine in which the opening and closing of a valve is carried out by a swinging rocker arm, a plurality of hydraulic lash adjusters (referred hereafter as lash adjusters) are arranged along a direction (a length direction) in which cylinders are arranged. This lash adjuster is made such that oil is supplied at a prescribed pressure from an oil pump arranged at a lower portion of the engine. Then, the lash adjuster has an effect of canceling the valve clearance caused by the thermal expansion of the valve, for example, by adjusting a position of the valve by utilizing the oil pressure of the oil during the engine operation. In the lash adjuster, an oil passage for the oil pumped from the oil pump of the engine is passing. The oil passage is formed in the cylinder block and the cylinder head. In the conventional engine, the oil passage formed in the cylinder head such that it is in communication with the oil pump side is positioned at a lower position than the oil passage to the lash adjuster. For this reason, in the conventional engine, the oil present in the oil passage from the oil pump to the lash adjuster at a time of the engine stop has been such that it flows down to the lower portion side of the engine, via this oil passage. Consequently, in the conventional engine, the sufficient oil is not supplied to the lash adjuster at a time of the engine re-start, which becomes a cause for generating a remaining air inside a hydraulic chamber inside the lash adjuster, and there has been a danger of adversely affecting the opening and closing of the valve.
As a measure against such a problem, there is known a lubrication device in which the oil passage provided toward the lash adjuster from the lower portion side of the cylinder head is equipped with an upper oil passage extending to an upper side than the lash adjuster, and a return oil passage that returns from this upper oil passage to a lower side and reaches to the lash adjuster (see Japanese Patent Application Publication No. H5-306603, for example). In this lubrication device, the oil supply to the lash adjuster from the return oil passage becomes possible at a time of the engine re-start. In this prior art, the oil is supplied to both the lash adjuster of the intake side (also referred to as the air intake herein) and the lash adjuster of the exhaust side, so that a communication pipe for making the oil passage of the air intake side and the oil passage of the exhaust side in communication is added to a space inside the cylinder head cover. At the both end portions of this communication pipe, flanges are provided, and these flanges are fixed to an upper end surface of the cylinder head by bolts.
However, in the above noted prior art, the communication pipe is arranged in a space between the upper end surface of the cylinder head and the cylinder head cover, so that it has been one in which the communication pipe is easily oscillated by the vibration of the engine. For this reason, at the flanges of the both end portions of the communication pipe, there has been a danger of having the oil flowing out due to the loosening of the bolts. Also, in such a prior art, the assembling work for bolting the communication pipe to the upper end surface of the cylinder head is cumbersome.